Summary: Sprint’s future largely rides on the iPhone. If the bet works, Sprint will be in a better position. If Sprint stumbles it will be on the financial ropes.

Sprint is getting the iPhone, but it’s going to cost the company about $20 billion in an all-or-nothing bet Apple’s iconic device.

According to the Wall Street Journal, Sprint has agreed to buy at least 30.5 million iPhones over the next four years. That is a staggering number of iPhones. Sprint is likely to lose money until 2014.

If Sprint is correct in its bet, the iPhone will put the carrier in a better position to gain customers and the recurring revenue they bring. If Sprint’s bet is wrong the company will find itself on the ropes.

For Sprint’s bet to work, it will have to sell nearly 8 million iPhones a year. What’s unclear is whether Sprint can activate that many iPhones. For instance, Verizon activated roughly 2 million iPhones in its two quarters since acquiring the device. AT&T activates more iPhones a quarter—3.6 million in the last two quarters—but that includes the iPhone 3GS, which runs $49.99.

If Sprint sells two iPhones—a premium and lower cost one—its bet may pay off. However, Sprint will face iPhone demand spread across all three carriers. Sprint may keep its current customers, but not land new ones. If Sprint is forced to change its iPhone mix for the Apple deal it will be swapping profitable Android phones for a loss leading iPhone.

Toss in the Sprint costs to acquire the iPhone as well as the potential network costs and the carrier is making a bet with the devil. It’s not clear that Sprint’s balance sheet can take the hit.

As of June 30, Sprint had long-term debt of $17.3 billion and cash of $4.27 billion. Sprint’s return on equity is -20.97 percent while Verizon’s is 13.7 percent and AT&T’s is 18.78 percent.

And if you consider Sprint’s Clearwire potential financial time bomb, the iPhone bet looks a bit crazy.

Hedging on the side of caution, Paczkowski has long claimed through sources of his own that thelaunch will be in October. Sources say that the iPhone will be made available for purchase within a few weeks after the announcement.

There has been wide speculation over the device, which is believed to have changed in screen size and dimensions. Other leaks point to a radical new design, whereas leaked device cases show that the smartphone will remain widely the same.

The truth is: Apple has done it again. We have no real idea what the next-generation iPhone will look like.

But while consumers will be looking for the new iPhone, as the highly anticipated Christmas and holiday season seller of the year, analysts and journalists will be looking at Tim Cook, who replaced Steve Jobs over the summer after he resigned from the company.

Cook will be in charge of the event, and no doubt will take to the stage as Apple’s new chief executive to announce the device. He has to be — he’s the boss. But Cook has never done this before, and will no doubt be aided by other executives to make their own announcement.

But as this may be Cook’s first presentation to the world, it has not been his first major challenge as chief executive.